Chemical Reaction Test 2

1.

The molecular-level representation illustrating solutions of the reactants lead (II) nitrate and potassium iodide is shown above. The reaction equation:Which of the following would be the best molecular level representation after the reaction has taken place?Choose carefully, (A) may not be the first one because of the scrambling of answers)

A.

A
B.

B
C.

C
D.

D

Correct Answer
D. D

Explanation
The correct answer is D because it shows the formation of solid lead iodide (PbI2) as a product of the reaction between lead (II) nitrate and potassium iodide. In the reaction, the lead (II) cations from lead (II) nitrate combine with the iodide anions from potassium iodide to form solid lead iodide. This is represented in option D, where the lead (II) cations are shown bonded with the iodide anions to form the solid product. Options A, B, and C do not accurately represent the formation of lead iodide as a product.

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2.

Consider 100.0 mL of a 1.0 M solution of NaCl in a beaker. After several days, you test the solution and find that it has a concentration of 1.33 M. How much water must have evaporation?

A.

20.0 mL
B.

25.0 mL
C.

75.0 mL
D.

80.0 mL

Correct Answer
A. 20.0 mL

Explanation
The concentration of a solution is defined as the amount of solute (in this case, NaCl) dissolved in a given volume of solvent (in this case, water). If the concentration of the solution increases after several days, it means that the amount of solute has remained the same while the volume of solvent has decreased. Therefore, the increase in concentration can be attributed to the evaporation of water from the solution. Since the concentration increased by 0.33 M, it means that 0.33 moles of NaCl are dissolved in the remaining volume of water. Using the equation C1V1 = C2V2, where C1 is the initial concentration, V1 is the initial volume, C2 is the final concentration, and V2 is the final volume, we can calculate the volume of water that evaporated to be 20.0 mL.

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3.

Which of the following statements is true concerning real gases?

A.

The observed pressure will be less than the ideal pressure, and the volume available for the gas particles is less than the volume of the container.
B.

The observed pressure will be less than the ideal pressure, and the volume available for the gas particles is greater than the volume of the container.
C.

The observed pressure will be greater than the ideal pressure, and the volume available for the gas particles is greater than the volume of the container.
D.

The observed pressure will be greater than the ideal pressure, and the volume available for thee gas particles is less than the volume of the container.

Correct Answer
A. The observed pressure will be less than the ideal pressure, and the volume available for the gas particles is less than the volume of the container.

Explanation
Real gases deviate from ideal gas behavior at high pressures and low temperatures. In real gases, the gas particles have volume and experience intermolecular forces, unlike in ideal gases where the particles are assumed to have no volume and no intermolecular forces. Due to these factors, the observed pressure of a real gas will be less than the ideal pressure because the gas particles occupy space and exert a repulsive force on each other. Additionally, the volume available for the gas particles will be less than the volume of the container because the gas particles occupy space themselves.

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4.

A sample of neon gas is contained in the left hand bulb and a sample of helium gas is contained in the right hand bulb of a two bulb container connected by a valve, as shown in the diagram. Initially the valve is closed.The left hand bulb has a volume of 9.00 L, and the Ne gas is at a pressure of 2.00 atm. The right hand bulb has a volume of 3.00L, and the He gas is at a pressure of 4.00 atm. After the valve is opened, what is true about the relative partial pressures of helium and neon? Assume constant temperature.

A.

The partial pressure of helium is 1.50 times as great as the partial pressure of neon
B.

The partial pressure of neon is 2.00 times as great as the partial pressure of helium
C.

The partial pressure of neon is 1.50 times as great as the partial pressure of helium
D.

The partial pressure of helium is 2.00 times as great as the partial pressure of neon

Correct Answer
C. The partial pressure of neon is 1.50 times as great as the partial pressure of helium

Explanation
When the valve is opened and the gases mix, the total pressure in the container will be the sum of the partial pressures of neon and helium. Since the volume of the left hand bulb is larger than the right hand bulb, the neon gas will occupy a greater volume and therefore contribute more to the total pressure. As a result, the partial pressure of neon will be greater than the partial pressure of helium. The ratio between the partial pressures can be calculated by dividing the volume of the left hand bulb by the volume of the right hand bulb, which gives a ratio of 3:1. Therefore, the partial pressure of neon is 1.50 times as great as the partial pressure of helium.

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5.

The boiling points of hydrogen chloride and hydrogen bromide are given in the table below. Based on periodicity and intermolecular forces, which of the other two hydrogen halides would have a boiling point that is higher than that of HBr?CompoundHClHBrHiHFBoiling Point (degrees celsius)-85-66??

A.

HI Only
B.

HF Only
C.

HI and HF
D.

Neither HI nor HF

Correct Answer
C. HI and HF

Explanation
Based on periodicity and intermolecular forces, the boiling point of a compound depends on the strength of the intermolecular forces between its molecules. The strength of these forces is determined by the polarity of the molecule and the size of its atoms. In this case, hydrogen fluoride (HF) and hydrogen iodide (HI) would have higher boiling points than hydrogen bromide (HBr) because they have stronger intermolecular forces. HF is a polar molecule and can form strong hydrogen bonds, while HI is a larger molecule with stronger London dispersion forces. Therefore, the correct answer is HI and HF.

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6.

Based on molecular structure and intermolecular forces, which of these substances would you predict to have the greatest viscosity?(Choose carefully)

A.

A
B.

B
C.

C
D.

D

Correct Answer
C. C

Explanation
Based on molecular structure and intermolecular forces, substance C would be predicted to have the greatest viscosity. This is because substances with larger and more complex molecules tend to have stronger intermolecular forces, which in turn leads to higher viscosity. Additionally, substances with higher molecular weight also tend to have higher viscosity. Therefore, substance C, which likely has larger and more complex molecules compared to the other substances, would be expected to have the greatest viscosity.

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